The present invention relates to a sheet-fed rotary printing machine provided with a driving system.
From prior art, for example from the German Pat. No. 2,334,177, sheet-fed rotary printing machines are known which include a sheet feeder, a series of printing units wherein the first printing unit cooperates with the feeder and the last printing unit cooperates with a discharger for printed sheets, a gear train for interconnecting impression cylinders and transfer cylinders of respective printing units, and a driving system provided with at least one driving element for transmitting parts of driving power to the gear train.
In modern printing industry employing sheet-fed rotary printing machines, there has been trend towards more and more structural alternations of the machines in order to rationalize and increase quality of the processed order. Continuously increasing demand is for printed products of highest quality having brilliant colors whereby in one running through the machine there is produced for example a four color first printing on the front side and two colors printing on the backside followed with a surface finish by varnishing and drying the varnish and the paint coat. Due to the consistent paints and viscous varnishes employed for this purpose power input in the machine is simultaneously increased and so are the static as well as dynamic forces acting on the machine. As a result of the higher loads of such multi-color printing machines there is a tendency to develop interfering low frequency vibrations which impair particularly the quality of the sheet transfer from one printing unit to another because the engagement of the toothed flanks in the gear train of the impression cylinders and transfer cylinders is disturbed.
Therefore, it is disadvantageous that in prior art driving systems for the heavily loaded printing machines, a continuous contact or engagement between the flanks is no longer guaranteed under the beforedescribed conditions. To avoid this drawback in series connected drives an overdimensioning of the driving gears would be necessary which would result in steep increase of construction costs. In addition, in printing machines having a plurality of printing units, such as for example a ten color printing machine, it is also disadvantageous that with increasing printing power the intake printing unit and the discharging printing unit run out of register.